A mobile communication signal in wireless communication systems is transmitted between a base station (BS) to a mobile station (MS), e.g., a mobile phone or device. This signal may be reflected off numerous scattering objects, such as buildings or structures, before reaching the MS. As a result of these reflections, the wireless communication signal may propagate over many paths before reaching the MS or BS, for example. These reflected signals or multipath replicas represent replicas of the original wireless communication signal and arrive at the MS with variations in signal power levels, and times, due to varying signal propagation lengths. Upon receipt, the originally transmitted communication signal and the multipath replicas are filtered, despread, recombined and decoded to give the voice or data signal originally sent.
To search for the wireless communication signal, a multipath signal searcher is employed, along with a rake receiver in a CDMA communication system with the multipath signal searcher. The wireless communication signal is searched over a search window having a plurality of time offsets. The multipath signal searcher includes numerous search paths, each separately searching for the wireless (RF) communication signal at a particular time offset within the search window. The time offsets correspond to pseudo noise offsets in CDMA systems. In typical systems, the search paths within a multipath signal searcher function in either serial or parallel modes.
In serial operation, the multipath signal searcher searches through the first half of the search window for the mobile communication signal by having all the search paths within the multipath signal searcher search only those time offsets over the first half of the search window. The first half is searched in one search time slot and the remaining portion of the search window, or second half of the search window, is searched in the next search time slot. An integration period of a number of power control-groups (PCGs) in length-represents the entire non-coherent accumulation of a search metric over the integration period or the integration period can represent that a search metric may be coherently accumulated within different PCGs and non-coherently accumulated over the entire integration period. It takes a second integration period to search the remaining time offsets. With parallel operation, the searcher is able to search the entire window in one search time slot.
A multipath searcher in a code division multiple access (CDMA) system functions to identify valid multipath energy peaks in a wireless environment. Multipath searcher resolution is a critical parameter in mobile equipment designs. The higher the resolution, the better the multipath searcher performance. Higher resolution multipath searches will take more time and use more hardware resources than low resolution searches. Longer search times and more hardware resource requirements result in greater power consumption.